Temperature sensors

ABSTRACT

The temperature sensor includes a voltage generator and a temperature code generator. The voltage generator includes a first temperature element having a first resistance value and a second temperature element having a second resistance value and utilizes the first and second temperature elements to generate a temperature voltage signal having a voltage level that varies according to a variation in temperature. The voltage generator generates a reference voltage signal having a substantially constant voltage level regardless of the variation in temperature. The temperature code generator compares a voltage level of the temperature voltage signal with a voltage level of the reference voltage signal to generate a plurality of temperature code signals including information on the variation in temperature based on the comparison.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application of U.S. applicationSer. No. 14/299,660, filed on Jun. 9, 2014, and claims priority under 35U.S.C 119(a) to Korean Application No. 10-2014-0010069, filed on Jan.28, 2014, in the Korean Intellectual Property Office, which isincorporated herein by reference in its entirety as set forth in full.

BACKGROUND

1. Technical Field

Embodiments relate to temperature sensors.

2. Related Art

With the development of increasingly higher performance electronicsystems, such as for example personal computers and communicationsystems, in the electronics industry, the demand for relatively fastermemory devices with higher integration characteristics are on the rise.An example of such a memory device is a dynamic random access memorydevice (DRAM). When semiconductor devices, such as the DRAM devices, areused in cellular phones and notebook computers, the semiconductordevices are often designed to have relatively low power consumptioncharacteristics. Efforts have been directed towards reducing theoperating current and the standby current of the semiconductor devices.

The data retention characteristic of DRAM cells including a singletransistor and a single storage capacitor may be relatively sensitive tovariations in temperature. In many cases, the operating conditions ofthe internal circuit blocks in a semiconductor integrated circuit may beadjusted based on variations in circumferential temperatures. Forexample, DRAM devices employed in mobile systems may be designed toadjust a refresh cycle time according to variations in thecircumferential temperature. Temperature sensors, such as digitaltemperature sensor regulators (DTSRs) and analog temperature sensorregulators (ATSRs), are often used to adjust the operating conditions ofsemiconductor devices, such as DRAM devices, in response to variationsin circumferential temperatures. Temperature sensors may detect arelatively high temperature and the operation cycle time may be adjustedto reduce power consumption in a self-refresh mode. The temperaturesensors may monitor circumferential temperatures in a normal operationmode.

SUMMARY

In an embodiment, a temperature sensor includes a voltage generator anda temperature code generator. The voltage generator includes a firsttemperature element having a first resistance value and a secondtemperature element having a second resistance value and utilizes thefirst and second temperature elements to generate a temperature voltagesignal having a voltage level that varies according to a variation intemperature. The voltage generator generates a reference voltage signalhaving a substantially constant voltage level regardless of thevariation in temperature. The temperature code generator compares avoltage level of the temperature voltage signal with a voltage level ofthe reference voltage signal and generates a plurality of temperaturecode signals including information on the variation in temperature basedon the comparison.

In an embodiment, a temperature sensor includes a voltage generator anda temperature code generator. The voltage generator utilizes first,second, third and fourth temperature elements having differentresistance values to generate a pre-temperature voltage signal having avoltage level that varies according to a variation in temperature. Thevoltage generator adjusts a voltage level of the pre-temperature voltagesignal to generate a temperature voltage signal. The voltage generatorgenerates a reference voltage signal having a substantially constantvoltage level regardless of the variation in temperature. Thetemperature code generator compares a voltage level of the temperaturevoltage signal with a voltage level of the reference voltage signal andgenerates a plurality of temperature code signals including informationon the variation in temperature based on the comparison.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram representation of an embodiment of atemperature sensor;

FIG. 2 is a circuit diagram representation of a voltage generator of thetemperature sensor of FIG. 1;

FIG. 3 is a block diagram representation of a temperature code generatorof the temperature sensor of FIG. 1; and

FIG. 4 is a circuit diagram representation of a voltage generator of anembodiment of a temperature sensor; and

FIG. 5 is a block diagram representation of a system including asemiconductor memory device including an embodiment of a temperaturesensor.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various embodiments will be described hereinafter with reference to theaccompanying drawings. The embodiments described herein are forillustrative purposes.

Referring to FIG. 1, an embodiment of a temperature sensor may include avoltage generator 10 and a temperature code generator 20.

The voltage generator 10 may include a first temperature element (N12shown in FIG. 2) having a first resistance value and a secondtemperature element (N13 shown in FIG. 2) having a second resistancevalue. The voltage generator 10 may utilize the first and secondtemperature elements N12, N13 to generate a temperature voltage signalVPTAT. The level of the temperature voltage signal VPTAT variesaccording to variations in temperature. The voltage generator 10 maygenerate a reference voltage signal VREF having a relatively constantvoltage level regardless of the value of the temperature. The generationof the temperature voltage signal VPTAT using the first and secondresistance values of the first and second temperature elements N12, N13will be described below. A voltage level of the temperature voltagesignal VPTAT may be set to increase or decrease in response to a rise inthe temperature.

The temperature code generator 20 may compare a level of the temperaturevoltage signal VPTAT with a level of the reference voltage signal VREFand responsively generate a plurality of temperature code signalsTCODE<1:N>. The temperature code signals TCODE<1:N> may includeinformation on temperature variation.

Referring to FIG. 2, the voltage generator 10 may include a drivevoltage generator 11, a reference voltage generator 12 and a driver 13.

The drive voltage generator 11 may generate a drive voltage signal DRVhaving a relatively constant voltage level regardless of variations intemperature. The drive voltage generator 11 may be implemented using aband gap voltage generation circuit or a Widlar voltage generationcircuit.

The reference voltage generator 12 may include a first drive element P11and a second drive element N11. The first drive element P11 and thesecond drive element N11 are electrically coupled in series. The firstdrive element P11 may be electrically coupled between a power supplyvoltage VDD terminal and a node ND10 and supply electric charge from thepower supply voltage VDD terminal to the node ND10 based on a voltagelevel of the drive voltage signal DRV. An example of the first driveelement is a PMOS transistor. The second drive element N11 may beelectrically coupled between the node ND10 and a ground voltage VSSterminal. An example of the second drive elements N11 is a NMOStransistor. A gate of the NMOS transistor N11 may be electricallycoupled to the node ND10 such that the NMOS transistor N11 operates in asaturation region. The NMOS transistor N11 may be turned on in responseto a voltage level of the node ND10. The second drive element N11 may beimplemented using a saturated NMOS transistor acting as a diode togenerate a constant current regardless of variations in temperature. Thereference voltage generator 12 may output the reference voltage signalVREF having a constant voltage level via the node ND10 regardless ofvariations in temperature.

The driver 13 may include a third drive element P12, a first temperatureelement N12 and a second temperature element N13. An example of thethird drive element P12 is a PMOS transistor. An example of the firsttemperature element N12 is an NMOS transistor. An example of the secondtemperature element N13 is an NMOS transistor. The third drive elementP12 may be electrically coupled between the power supply voltage VDDterminal and a node ND11 and supply electric charge from the powersupply voltage VDD terminal to the node ND11 based on a voltage level ofthe drive voltage signal DRV. The first temperature element N12 may beelectrically coupled between the node ND11 and a node ND12. Thetemperature voltage signal VPTAT is generated at the node ND12. A gateof the NMOS transistor N12 may be electrically coupled to the node ND11such that the NMOS transistor N12 operates in a saturation region to actas a diode. The first temperature element N12 may be turned on inresponse to a voltage level at the node ND11. The second temperatureelement N13 may be electrically coupled between the node ND12 and theground voltage VSS terminal. A gate of the NMOS transistor N13 may beelectrically coupled to the node ND11. The second temperature elementN13 may be turned on in response to a voltage level at the node ND11.The first temperature element N12 may be configured such that a currentflowing through the first temperature element N12 increases or decreasesas the temperature rises. Similarly, the second temperature element N13may be configured such that a current flowing through the secondtemperature element N13 increases or decreases as the temperature rises.

An operation for adjusting a voltage level of the temperature voltagesignal VPTAT based on the first and second resistance values of thefirst and second temperature elements N12, N13, respectively, will bedescribed with reference to an example where the first and secondtemperature elements N12, N13 operate in a saturation mode in responseto a voltage at the node ND11 to generate substantially the samecurrent.

The operation for setting the resistance values of the first and secondtemperature elements N12, N13 will be described hereinafter.

The first resistance value of the first temperature element N12 may beadjusted based on a threshold voltage of the first temperature elementN12 or according to a ratio of a channel length and a channel width ofthe first temperature element N12. Similarly, the second resistancevalue of the second temperature element N13 may be adjusted based on athreshold voltage of the second temperature element N13 or according toa ratio of a channel length and a channel width of the secondtemperature element.

The operation for adjusting a voltage level of the temperature voltagesignal VPTAT will be described hereinafter.

A voltage level of the node ND11 may be divided by the resistance valuesof the first and second temperature elements N12, N13 where the firstand second temperature elements N12, N13 are serially electricallycoupled between the node ND11 and the ground voltage VSS terminal. Thetemperature voltage signal VPTAT may be generated from the node ND12where the node ND12 is electrically coupled between the first and secondtemperature elements N12, N13. The voltage level of the temperaturevoltage signal VPTAT may be adjusted based on the resistance values ofthe first and second temperature elements N12, N13.

Referring to FIG. 3, the temperature code generator 20 may include acomparison voltage generator 21, a comparator 22 and a buffer 23.

The comparison voltage generator 21 may receive the reference voltagesignal VREF as an input and responsively generate a plurality ofcomparison voltage signals VCOM<1:N>. The voltage level of eachsequential comparison voltage signal of the plurality of comparisonvoltage signals VCOM<1:N> is relatively higher. The comparison voltagegenerator 21 may be implemented using, for example, a voltage divisioncircuit that generates a plurality of voltage signals where eachsequential voltage signal of the plurality of voltage signals isrelatively higher.

The comparator 22 may compare each of the plurality of comparisonvoltage signals VCOM<1:N> with the temperature voltage signal VPTAT togenerate a plurality of comparison signals COMP<1:N>. The comparator 22may be implemented using an analog to digital converter (ADC) where theanalog to digital converter (ADC) coverts a plurality of input voltagelevels into a plurality of digital signals.

The buffer 23 may buffer the plurality of comparison signals COMP<1:N>to generated a plurality of buffered comparison signals COMP<1:N> as aplurality of temperature code signals TCODE<1:N>.

An operation of the temperature sensor having the aforementionedconfiguration will be described hereinafter with reference to FIGS. 1, 2and 3 in conjunction with an example where the second resistance valueof the second temperature element N13 is set to be relatively greaterthan the first resistance value of the first temperature element N12 inthe generation of the temperature voltage signal VPTAT.

The drive voltage generator 11 may generate a drive voltage signal DRVhaving a relatively constant voltage level regardless of variations intemperature.

The first drive element P11 of the reference voltage generator 12 maysupply electric charges from the power supply voltage VDD terminal tothe node ND10 based on the voltage level of the drive voltage signalDRV. The second drive element N11 may be turned on in response to thevoltage level at the node ND10. The reference voltage generator 12 mayoutput the reference voltage signal VREF having a relatively constantvoltage level via the node ND10 where the reference voltage signal VREFhas a relatively constant voltage level regardless of variations intemperature.

The third drive element P12 of the driver 13 may supply electric chargesfrom the power supply voltage VDD terminal to the node ND11 based on thevoltage level of the drive voltage signal DRV. The first temperatureelement N12 may be turned on in response to a voltage level at the nodeND11. Since the second resistance value of the second temperatureelement N13 is relatively greater than the first resistance value of thefirst temperature element N12, a voltage level of the node ND12 may berelatively higher than the voltage level of the temperature voltagesignal VPTAT when the first and second temperature elements N12, N13have substantially the same resistance value. The voltage level at theode ND12 is the voltage level of the temperature voltage signal VPTAT.The voltage level of the temperature voltage signal VPTAT may graduallyincrease as the second resistance value of the second temperatureelement N13 increases.

The comparison voltage generator 21 may receive the reference voltagesignal VREF as a input and responsively generate the plurality ofcomparison voltage signals VCOM<1:N The voltage level of each sequentialcomparison voltage signal of the plurality of comparison voltage signalsVCOM<1:N> is relatively higher.

The comparator 22 may compare each of the plurality of comparisonvoltage signals VCOM<1:N> with the temperature voltage signal VPTAT togenerate the plurality of comparison signals COMP<1:N>.

The buffer 23 may buffer the plurality of comparison signals COMP<1:N>and output the buffered comparison signals COMP<1:N> as the plurality oftemperature code signals TCODE<1:N>.

As described above, an embodiment of a temperature sensor may adjust theresistance values of the first and second temperature elements N12, N13to increase a variation of a voltage level of the temperature voltagesignal VPTAT where the voltage level of the temperature voltage signalVPTAT varies according to variations in temperature. The temperaturesensor may generate the temperature code signals TCODE<1:N>based on thetemperature voltage signal VPTAT and may improve the reliability ofinformation regarding variations in the temperature.

FIG. 4 is a circuit diagram representation of a voltage generator 10 ain an embodiment of a temperature sensor. The voltage generator 10 inthe temperature sensor 10 may be replaced with the voltage generator 10a shown in FIG. 4.

The voltage generator 10 a may include a drive voltage generator 14, areference voltage generator 15, a first driver 16 and a second driver17.

The drive voltage generator 14 may generate a drive voltage signal DRVhaving a substantially constant voltage level regardless of variationsin temperature. The drive voltage generator 14 may be implemented usinga band gap voltage generation circuit or a Widlar voltage generationcircuit.

The reference voltage generator 15 may include a first drive element P13and a second drive element N14 electrically coupled in series. The firstdrive element P13 may be electrically coupled between a power supplyvoltage VDD terminal and a node ND13 and supply electric charge from thepower supply voltage VDD terminal to the node ND13 based on a voltagelevel of the drive voltage signal DRV. An example of the first driveelement P13 is a PMOS transistor. An example of the second drive elementN14 is an NMOS transistor. The second drive element N14 may beelectrically coupled between the node ND13 and a ground voltage VSSterminal. A gate of the

NMOS transistor N14 may be electrically coupled to the node ND13 suchthat the NMOS transistor N14 operates in a saturation region. The NMOStransistor N14 may be turned on according to a voltage level at the nodeND13. The second drive element N14 may be implemented using a saturatedNMOS transistor acting as a diode to generate a substantially constantcurrent regardless of variations in temperature. The reference voltagegenerator 14 may output a reference voltage signal VREF having asubstantially constant voltage level through the node ND13 regardless ofvariations in temperature.

The first driver 16 may include a third drive element P14, a firsttemperature element N15 and a second temperature element N16. The thirddrive element P14 may be electrically coupled between the power supplyvoltage VDD terminal and a node ND14 and supply electric charge from thepower supply voltage VDD terminal to the node ND14 based on a voltagelevel of the drive voltage signal DRV. An example of the third driveelement P14 is a PMOS transistor. An example of the first temperatureelement N15 is an NMOS transistor. An example of the second temperatureelement N16 is an NMOS transistor. The first temperature element N15 maybe electrically coupled between the node ND14 and a node ND15. Apre-temperature voltage signal PVPTAT is generated at the node ND15. Agate of the NMOS transistor N15 may be electrically coupled to the nodeND14 such that the NMOS transistor N15 operates in a saturation regionto act as a diode. The first temperature element N15 may be turned on inresponse to a voltage level at the node ND14. The second temperatureelement N16 may be electrically coupled between the node ND15 and theground voltage VSS terminal. A gate of the NMOS transistor N16 may beelectrically coupled to the node ND14. The second temperature elementN16 may be turned on in response to a voltage level at the node ND14.The first temperature element N15 may be configured such that a currentflowing through the first temperature element N15 increases or decreasesas the temperature rises. Similarly, the second temperature element N16may be configured such that a current flowing through the secondtemperature element N16 increases or decreases as the temperature rises.

The second driver 17 may include a fourth drive element P15, a thirdtemperature element N17 and a fourth temperature element N18. An exampleof the fourth drive element P15 is a PMOS transistor. An example of thethird temperature element N17 is an NMOS transistor. An example of thefourth temperature element N18 is an NMOS transistor. The fourth driveelement P15 may be electrically coupled between the power supply voltageVDD terminal and a node ND16 and supply electric charge from the powersupply voltage VDD terminal to the node ND16 according to a voltagelevel of the drive voltage signal DRV. The third temperature element N17may be electrically coupled between the node ND16 and a node ND17. Atemperature voltage signal VPTAT is output at the node ND17. A gate ofthe NMOS transistor N17 may be electrically coupled to the node ND16such that the NMOS transistor N17 operates in a saturation region to actas a diode. The third temperature element N17 may be turned on inresponse to a voltage level at the node ND16. The fourth temperatureelement N18 may be electrically coupled between the node ND17 and thenode ND15. The pre-temperature voltage signal PVPTAT is output at thenode ND15. A gate of the NMOS transistor N18 may be electrically coupledto the node ND16. The fourth temperature element N18 may be turned on inresponse to a voltage level at the node ND16. The third temperatureelement N17 may be configured such that a current flowing through thethird temperature element N17 increases or decreases as the temperaturerises. Similarly, the fourth temperature element N18 may be configuredsuch that a current flowing through the fourth temperature element N18increases or decreases as the temperature rises.

Operations for generating the pre-temperature voltage PVPTAT where thevoltage level of the pre-temperature voltage PVPTAT varies according tovariations in temperature using the first and second temperatureelements N15, N16 will be described below. Operations for generating thetemperature voltage VPTAT by adjusting the voltage level of thepre-temperature voltage PVPTAT using the third and fourth temperatureelements N17, N18 will be described hereinafter. An example where thefirst, second, third and fourth temperature elements N15, N16, N17, N18have different resistance values and may operate in a saturation mode togenerate substantially the same current with be used in thedescriptions.

An operation for setting the resistance values of the first, second,third and fourth temperature elements N15, N16, N17, N18 will bedescribed hereinafter.

The resistance value of the first temperature element N15 may beadjusted based on a threshold voltage of the first temperature elementN15 or based on a ratio of a channel length and a channel width of thefirst temperature element N15. The resistance value of the secondtemperature element N16 may be adjusted based on a threshold voltage ofthe second temperature element N16 or based on a ratio of a channellength and a channel width of the second temperature element N16. Theresistance value of the third temperature element N17 may be adjustedbased on a threshold voltage of the third temperature element N17 orbased on a ratio of a channel length and a channel width of the thirdtemperature element N17. The resistance value of the fourth temperatureelement N18 may be adjusted based on a threshold voltage of the fourthtemperature element N18 or based on a ratio of a channel length and achannel width of the fourth temperature element N18.

An operation for adjusting a voltage level of the pre-temperaturevoltage signal PVPTAT will be described hereinafter.

A voltage level of the node ND14 may be divided by the resistance valuesof the first and second temperature elements N15, N16 where the firstand second temperature elements N15, N16 are serially electricallycoupled between the node ND14 and the ground voltage VSS terminal. Thepre-temperature voltage signal PVPTAT may be output at the node ND15between the first and second temperature elements N12. The voltage levelof the pre-temperature voltage signal PVPTAT may be adjusted based onthe resistance values of the first and second temperature elements N15,N16.

An operation for adjusting a voltage level of the temperature voltagesignal VPTAT will be described hereinafter.

A voltage level of the temperature voltage signal VPTAT may be adjustedbased on the resistance values of the third and fourth temperatureelements N17, N18, where the third and fourth temperature elements N17,N18 are serially electrically coupled between the node ND16 and the nodeND15. A voltage level at the node ND15 may correspond to the voltagelevel of the pre-temperature voltage signal PVPTAT. The voltage level ofthe temperature voltage signal VPTAT may be relatively higher than thevoltage level at the node ND15. The temperature voltage signal VPTAT maybe generated to have a relatively higher voltage level than the voltagelevel of the pre-temperature voltage signal PVPTAT.

An operation of the temperature sensor including the voltage generator10 a having the aforementioned configuration will be described withreference to FIGS. 1, 3, and 4 in conjunction with an example where thefirst second, third and fourth temperature elements N15, N16, N17, N18have different resistance values and the temperature voltage signalVPTAT is generated by adjusting a voltage level of the pre-temperaturevoltage signal PVPTAT with the first, second, third and fourthtemperature elements N15, N16, N17, N18.

The drive voltage generator 14 may generate the drive voltage signal DRVhaving a substantially constant voltage level regardless of thevariation in temperature.

The first drive element P13 of the reference voltage generator 15 maysupply electric charge from the power supply voltage VDD terminal to thenode ND13 based on a voltage level of the drive voltage signal DRV. Thesecond drive element N14 may be turned on in response to a voltage levelat the node ND13. The reference voltage generator 15 may output thereference voltage signal VREF having a substantially constant voltagelevel at the node ND13 regardless of variations in the temperature.

The third drive element P14 of the first driver 16 may supply electriccharge from the power supply voltage VDD terminal to the node ND14 basedon a voltage level of the drive voltage signal DRV. The firsttemperature element N15 may be turned on in response to a voltage levelat the node ND14. The second temperature element N16 may be turned on inresponse to a voltage level at the node ND14. A voltage level of thepre-temperature voltage signal PVPTAT may be adjusted according to theresistance values of the first and second temperature elements N15, N16.

The fourth drive element P15 of the second driver 17 may supply electriccharge from the power supply voltage VDD terminal to the node ND16 basedon a voltage level of the drive voltage signal DRV. The thirdtemperature element N17 may be turned on in response to a voltage levelat the node ND16. The fourth temperature element N18 may be turned on inresponse to a voltage level at the node ND16. A voltage level of thetemperature voltage signal VPTAT may be adjusted according to theresistance values of the third and fourth temperature elements N17, N18where the third and fourth temperature elements N17, N18 are seriallyelectrically coupled between the node ND16 and the node ND15. A voltagelevel at the node ND15 may correspond to the voltage level of thepre-temperature voltage signal PVPTAT. The voltage level of thetemperature voltage signal VPTAT may be relatively higher than thevoltage level at the node ND15. The temperature voltage signal VPTAT maybe generated to have a voltage level that is higher than the voltagelevel of the pre-temperature voltage signal PVPTAT.

The comparison voltage generator 21 may receive the reference voltagesignal VREF as an input and responsively generate the plurality ofcomparison voltage signals VCOM<1:N>. The voltage level of eachsequential comparison voltage signal of the plurality of comparisonvoltage signals VCOM<1:N> is relatively higher.

The comparator 22 may compare each of the plurality of comparisonvoltage signals VCOM<1:N> with the temperature voltage signal VPTAT togenerate the plurality of comparison signals COMP<1:N>.

The buffer 23 may buffer the plurality of comparison signals COMP<1:N>and output the buffered comparison signals COMP<1:N> as the plurality oftemperature code signals TCODE<1:N>.

As described above, an embodiment of a temperature sensor may adjust avariation of a voltage level of the pre-temperature voltage signalPVPTAT where the voltage level of the pre-temperature voltage signalvaries according to variations in temperature using the resistancevalues of the first and second temperature elements N15, N16 Thetemperature sensor may increase a voltage level of the temperaturevoltage signal VPTAT by adjusting the voltage level of thepre-temperature voltage signal PVPTAT. An embodiment of the temperaturesensor may generate the temperature code signals TCODE<1:N> from thetemperature voltage signal VPTAT and may improve the reliability ofinformation on the temperature variation.

Referring to FIG. 5, a block diagram representation of a system 1000including an embodiment of a semiconductor device 1350 is shown. In anembodiment, the semiconductor device 1350 includes an embodiment of atemperature sensor. In an embodiment, the semiconductor device 1350 is asemiconductor memory device. The system 1000 includes one or moresemiconductor memory devices 1350 and a memory controller 1200.

An embodiment of the temperature sensor includes a voltage generator anda temperature code generator. The voltage generator includes a firsttemperature element having a first resistance value and a secondtemperature element having a second resistance value and utilizes thefirst and second temperature elements to generate a temperature voltagesignal having a voltage level that varies according to a variation in atemperature. The voltage generator generates a reference voltage signalhaving a substantially constant voltage level regardless of thevariation in temperature. The temperature code generator compares avoltage level of the temperature voltage signal with a voltage level ofthe reference voltage signal to generate a plurality of temperature codesignals including information on the variation in temperature based onthe comparison.

An embodiment of a temperature sensor includes a voltage generator and atemperature code generator. The voltage generator utilizes first,second, third and fourth temperature elements having differentresistance values to generate a pre-temperature voltage signal having avoltage level that varies according to a variation in temperature. Thevoltage generator adjusts a voltage level of the pre-temperature voltagesignal to generate a temperature voltage signal. The voltage generatorgenerates a reference voltage signal having a substantially constantvoltage level regardless of the variation in temperature. Thetemperature code generator compares a voltage level of the temperaturevoltage signal with a voltage level of the reference voltage signal andgenerates a plurality of temperature code signals including informationon the variation in temperature based on the comparison.

Examples of the semiconductor memory device 1350 include, but are notlimited to, dynamic random access memory, static random access memory,synchronous dynamic random access memory (SDRAM), synchronous graphicsrandom access memory (SGRAM), double data rate dynamic ram (DDR), anddouble data rate SDRAM.

The memory controller 1200 is used in the design of memory devices,processors, and computer systems. The system 1000 may include one ormore processors or central processing units (“CPUs”) 1100. The CPU 1100may be used individually or in combination with other CPUs. While theCPU 1100 will be referred to primarily in the singular, it will beunderstood by those skilled in the art that a system with any number ofphysical or logical CPUs may be implemented.

A chipset 1150 may be electrically coupled to the CPU 1100. The chipset1150 is a communication pathway for signals between the CPU 1100 andother components of the system 1000, which may include the memorycontroller 1200, an input/output (“I/O”) bus 1250, and a disk drivecontroller 1300. Depending on the configuration of the system 1000, anyone of a number of different signals may be transmitted through thechipset 1150, and those skilled in the art will appreciate that therouting of the signals throughout the system 1000 can be readilyadjusted without changing the underlying nature of the system.

The memory controller 1200 may be electrically coupled to the chipset1150. The memory controller 1200 can receive a request provided from theCPU 1100, through the chipset 1150. In alternate embodiments, the memorycontroller 1200 may be integrated into the chipset 1150. The memorycontroller 1200 may be electrically coupled to one or more memorydevices 1350. The memory devices 1350 may be any one of a number ofindustry standard memory types, including but not limited to, singleinline memory modules (“SIMMs”) and dual inline memory modules(“DIMMs”). The memory devices 1350 may facilitate the safe removal ofthe external data storage devices by storing both instructions and data.

The chipset 1150 may be electrically coupled to the I/O bus 1250. TheI/O bus 1250 may serve as a communication pathway for signals from thechipset 1150 to I/O devices 1410, 1420 and 1430. The I/O devices 1410,1420 and 1430 may include a mouse 1410, a video display 1420, or akeyboard 1430. The I/O bus 1250 may employ any one of a number ofcommunications protocols to communicate with the I/O devices 1410, 1420,and 1430. The I/O bus 1250 may be integrated into the chipset 1150.

The disk drive controller 1450 may also be electrically coupled to thechipset 1150. The disk drive controller 1450 may serve as thecommunication pathway between the chipset 1150 and one or more internaldisk drives 1450. The internal disk drive 1450 may facilitatedisconnection of the external data storage devices by storing bothinstructions and data. The disk drive controller 1300 and the internaldisk drives 1450 may communicate with each other or with the chipset1150 using virtually any type of communication protocol, including allof those mentioned above with regard to the I/O bus 1250.

The system 1000 described above in relation to FIG. 5 is merely oneexample of a system employing a semiconductor memory device 1350. Inalternate embodiments, such as cellular phones or digital cameras, thecomponents may differ from the embodiment shown in FIG. 5.

While certain embodiments have been described above, it will beunderstood to those skilled in the art that the embodiments describedare by way of example only. Accordingly, the temperature sensordescribed herein should not be limited based on the describedembodiments. Rather, the temperature sensor described herein should onlybe limited in light of the claims that follow when taken in conjunctionwith the above description and accompanying drawings.

What is claimed is:
 1. A temperature sensor comprising: a voltagegenerator comprising first, second, third and fourth temperatureelements having different resistance values and suitable for generatinga pre-temperature voltage signal having a voltage level that variesaccording to a variation in temperature, for adjusting a voltage levelof the pre-temperature voltage signal to generate a temperature voltagesignal, and for generating a reference voltage signal having asubstantially constant voltage level regardless of the variations intemperature; and a temperature code generator suitable for comparing avoltage level of the temperature voltage signal with a voltage level ofthe reference voltage signal to generate a plurality of temperature codesignals including information on the variation in temperature based onthe comparison.
 2. The temperature sensor of claim 1, wherein thevoltage generator comprises: a drive voltage generator suitable forgenerating a drive voltage signal having a substantially constantvoltage level regardless of the variation in temperature; a referencevoltage generator suitable for generating the reference voltage signalin response to the drive voltage signal; a first driver suitablecomprising the first and second temperature elements and suitable forgenerating the pre-temperature voltage signal in response to the drivevoltage signal; and a second driver comprising the third and fourthtemperature elements and suitable for generating the temperature voltagesignal from the pre- temperature voltage signal.
 3. The temperaturesensor of claim 2, wherein the reference voltage generator comprises: afirst drive element electrically coupled between a power supply voltageterminal and a first node and suitable for supplying electric chargefrom the power supply voltage terminal to the first node in response tothe drive voltage signal; and a second drive element electricallycoupled between the first node and a ground voltage terminal andsuitable for being turned on in response to a voltage level at the firstnode.
 4. The temperature sensor of claim 3, wherein the second driveelement is suitable for generating a constant current regardless of thevariation in temperature.
 5. The temperature sensor of claim 2, whereinthe first driver comprises: a third drive element electrically coupledbetween a power supply voltage terminal and a second node and suitablefor supplying electric charge from the power supply voltage terminal tothe second node in response to the drive voltage signal; the firsttemperature element electrically coupled between the second node and athird node wherein the pre-temperature voltage signal is output at thethird node and suitable for being turned on in response to a voltagelevel at the second node; and the second temperature elementelectrically coupled between the third node and a ground voltageterminal and suitable for being turned on in response to the voltagelevel at the second node.
 6. The temperature sensor of claim 5, whereina voltage level of the pre-temperature voltage signal is adjusted basedon the resistance values of the first and second temperature elements.7. The temperature sensor of claim 5, wherein the second drivercomprises: a fourth drive element electrically coupled between the powersupply voltage terminal and a fourth node and suitable for supplyingelectric charge from the power supply voltage terminal to the fourthnode in response to the drive voltage signal; the third temperatureelement electrically coupled between the fourth node and a fifth node,wherein the temperature voltage signal is output at the fifth node andsuitable for being turned on in response to a voltage level at thefourth node; and the second temperature element electrically coupledbetween the fifth node and the third node and suitable for being turnedon in response to the voltage level at the fourth node.
 8. Thetemperature sensor of claim 7, wherein a current flowing through thefirst temperature element varies according to the variation intemperature; wherein a current flowing through the second temperatureelement varies according to the variation in temperature; wherein acurrent flowing through the third temperature element varies accordingto the variation in temperature; and wherein a current flowing throughthe fourth temperature element varies according to the variation intemperature.
 9. The temperature sensor of claim 7, wherein a voltagelevel of the temperature voltage signal is adjusted based on theresistance values of the third and fourth temperature elements and avoltage level of the pre-temperature voltage signal.
 10. The temperaturesensor of claim 1, wherein the temperature code generator comprises: acomparison voltage generator suitable for receiving the referencevoltage signal to generate a plurality of comparison voltage signalswhose voltage levels sequentially increase; a comparator suitable forcomparing the plurality of comparison voltage signals with thetemperature voltage signal to generate a plurality of comparison signalsbased on the comparison; and a buffer suitable for buffering theplurality of comparison signals and for generating the bufferedcomparison signals as the plurality of temperature code signals.